Bone chapter (nontumor and tumor)
Osteosarcoma - variants
Low grade intraosseous (central) osteosarcoma

Author: David L. Stockman, M.D. (see Authors page)

Revised: 13 April 2016, last major update April 2016

Copyright: (c) 2003-2016, PathologyOutlines.com, Inc.

PubMed Search: Central low-grade osteosarcoma
Definition / General
  • Rare tumor (1% of osteosarcomas) with good prognosis
  • Develops during 2nd-5th decades of life
  • Similar in histologic appearance to surface low grade osteosarcoma (parosteal osteosarcoma)
  • Metastatic rate ~ 15% due to tumors that have undergone dedifferentiation
Sites
  • Femur is most commonly affected, followed by tibia
  • Typically centered in medullary cavity of metaphysis or metaphyseal-diaphyseal region of long tubular bone
Radiology Description
  • Poor margination with cortical disruption
  • Poorly demarcated margins with soft tissue extension
  • Variable matrix mineralization
Radiology Images

Images hosted on Pathout server:

Distal femur - contributed by Dr. Mark R. Wick

Treatment
  • En bloc resection
Gross Description
  • Little to no necrosis, resembles a low grade bone forming lesion
  • Cut surface is hard, gritty, tan-white
  • Poorly defined margins, may show cortical destruction with associated soft tissue extension
Micro Description
  • Low grade osteosarcoma composed of bland spindle shaped cells and mature bone
  • Paucicellular, infiltrates between bone trabeculae composed of interlacing fascicles of spindle cells with mild atypia and rare mitotic figures in heavy collagenous background
  • Moderate osteoid and immature bone formation
Micro Images

Images hosted on Pathout server:

Contributed by Dr. Mark R. Wick



Images hosted on Nature.com:

Heavy irregular bony trabeculae

Coalescing plates of tumor bone


Mosaic pattern of cement lines resembling Paget’s disease


Figure 6a: low grade features with cement lines in adjacent bone; 6b: high grade features of dedifferentiated tumor

Positive Stains
  • MDM2 positivity in 40% of cases, negative staining does not exclude osteosarcoma diagnosis, positive staining suggests malignancy
  • Must correlate with radiology and histology and get second opinion in these cases as treatment is resection
Differential Diagnosis